Efficient collection and concentration of radiant energy is useful in a number of applications and is of particular value for devices that convert solar energy to electrical, thermal or biofuel energy. The different types of solar energy conversions have different spectral requirements. Thus, thermal power generation from solar energy is spectrally insensitive, while photosynthesis and photovoltaic (PV) solar cells require specific spectral bands. It is thus possible to split the spectrum of solar energy to maximize use of the solar spectrum for the conversion. In other words, the solar energy is split so that the solar energy in the spectral band for photosynthesis and photovoltaic solar cells are used for conversion by photosynthesis and photoelectric conversion, while the rest of the solar spectrum is directed to thermal conversion.
Dichroic filters have been proposed for performing the function of splitting the solar spectrum. U.S. Pat. No. 7,741,557 discloses one technique using dichroic filters for splitting the solar spectrum. Dichroic filters however are made by individual deposition of hundreds of layers with specified indices of refraction and are quite fragile. This approach requires time and precision and is not economically viable for application to large areas of solar power conversion. Thus, dichroic filters are up to six times as expensive as conventional light filters.
Another material that splits light spectrum is luminescent dye. Luminescent dye can absorb and reflect specific wavelengths of light. However, dyes are plagued with many logistical issues. Among the problems with dyes are reabsorption losses, and inefficient use of the light spectrum. Dyes emit light in all directions and it may be difficult to utilize all of the light emitted by luminescent dyes.
Prisms may also be used for spectrum splitting, but is inefficient because prisms would separate all the bands in the solar spectrum, whereas separation of only one band may be all that is needed.
It is thus desirable to provide a mechanism and method for splitting the energy spectrum that are superior to the above noted techniques.